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4.0

Jun 29, 2018
06/18

by
Mamta Gulati; Tarun Deep Saini

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We present a modal analysis of instabilities of counter-rotating, self-gravitating collisionless stellar discs, using the recently introduced modified WKB formulation of spiral density waves for collisionless systems (Gulati \& Saini). The discs are assumed to be axisymmetric and in coplanar orbits around a massive object at the common center of the discs. The mass in both discs is assumed to be much smaller than the mass of the central object. For each disc, the disc particles are assumed...

Topics: Astrophysics, Astrophysics of Galaxies

Source: http://arxiv.org/abs/1602.07169

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42

Sep 21, 2013
09/13

by
Tarun Deep Saini; Mamta Gulati; S. Sridhar

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Thin accretion discs around massive compact objects can support slow pressure modes of oscillations in the linear regime that have azimuthal wavenumber $m=1$. We consider finite, flat discs composed of barotropic fluid for various surface density profiles and demonstrate--through WKB analysis and numerical solution of the eigenvalue problem--that these modes are stable and have spatial scales comparable to the size of the disc. We show that the eigenvalue equation can be mapped to a...

Source: http://arxiv.org/abs/0901.4229v2

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7.0

Jun 29, 2018
06/18

by
Mamta Gulati; Tarun Deep Saini

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The short--wave asymptotics (WKB) of spiral density waves in self-gravitating stellar discs is well suited for the study of the dynamics of tightly--wound wavepackets. But the textbook WKB theory is not well adapted to the study of the linear eigenmodes in a collisionless self-gravitating disc because of the transcendental nature of the dispersion relation. We present a modified WKB of spiral density waves, for collisionless discs in the epicyclic limit, in which the perturbed gravitational...

Topics: Astrophysics, Astrophysics of Galaxies

Source: http://arxiv.org/abs/1601.04148

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118

Jul 20, 2013
07/13

by
Mamta Gulati; Tarun Deep Saini; S. Sridhar

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We study the linear $m=1$ counter-rotating instability in a two-component, nearly Keplerian disc. Our goal is to understand these \emph{slow} modes in discs orbiting massive black holes in galactic nuclei. They are of interest not only because they are of large spatial scale--and can hence dominate observations--but also because they can be growing modes that are readily excited by accretion events. Self-gravity being nonlocal, the eigenvalue problem results in a pair of coupled integral...

Source: http://arxiv.org/abs/1203.2239v1